Subway's Creamy Sriracha sauce is something they're testing out here in southern California. I tried it out on a Chipotle Chicken & Cheese sub (with bell peppers, provolone cheese, and onions on flatbread) and compared it to the real thing.
The sub cost me $5 since it's the Featured $5 Footlong this month and I asked for the Creamy Sriracha in substitution for the Chipotle Southwest sauce.
When they were putting together my sandwich, they put one line of sauce across the sub; it didn't look like much so I asked them to put a second line, so what you're looking at in the pictures is a double helping of Creamy Sriracha sauce.
The Creamy Sriracha sauce is a little more sweet and tangy, but mutes the distinctive flavor of the chilies, which is much more pronounced in regular Sriracha. Heatwise, they are both pretty spicy, but the Creamy Sriracha might be just a little less spicy (I'm not sure as my tongue was already feeling a steady burn at this point). I'd recommend using either of them judiciously if you actually want to be able to taste your food.
I would not recommend Subway's' Creamy Sriracha sauce if you're just looking for a little bit of spicy or are averse to spicy foods. If you can stand the heat though, there's a nice flavor enhancement here to kick your favorite sub up a notch.